I bought this aluminum Thermostat housing for my Z3, then sold the car
before I got a chance to install it.
This housing replaces the plastic ones that are prone to heat damage and
cracking. It is the equivalent of BMW part number 11 53 1 722 531. I
think it fits a lot of different M50 and M52 engines from the early 90's
on. Check the part number of yours at http://www.realoem.com/bmw/ to
They sell for around $30. I forget what I paid, but if someone wants
to give me $15 and cover the shipping it's yours! Just send me an email
to fjwills at gmail dot com.